Bash 101 - to (do) ; or not to (do) ; ? Post: 303022252

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Top Forums Shell Programming and Scripting Bash 101 - to (do) ; or not to (do) ; ? Post 303022252 by bakunin on Tuesday 28th of August 2018 05:18:15 PM

08-28-2018

Registered User

Quote:

Originally Posted by annacreek

Code:

while [ $i -lt 4 ] do xterm & i=$[$i+1] done

I don't know from which "manual" you got that, but there are more errors then correct words in it. Shame on whoever wrote this drivel. The correct form would be:

Code:

while [ $i -lt 4 ] ; do xterm & ; (( i = i+1 )) ; done

or, in a more readable way:

Code:

while [ $i -lt 4 ] ; do
     xterm &
     (( i = i+1 ))
done

Note that [ is actually a real command: it is a different way to invoke /bin/test. Written in "long form" where the command is more easily recognisable it would be:

Code:

while /bin/test $i -lt 4 ; do
     xterm &
     (( i = i+1 ))
done

The command

Code:

/bin/test $i -lt 4

will return 0 (logical TRUE) if the variable i is lower than 4 and 1 (logically FALSE) otherwise. The while-loop is repeated as long as the control-command (in this case /bin/test) returns 0 and stops if it returns 1. The following will read a complete file:

Code:

while read LINE ; do
     echo "== $LINE =="
done < /some/file

because the read-command returns 0 as long as it can read a line but returns 1 when it hits end-of-file.

I hope this helps.

bakunin

bakunin

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COMMAND-NOT-FOUND(1)					    http://en.opensuse.org/Sco					      COMMAND-NOT-FOUND(1)

NAME

       command-not-found - A command-not-found handler

SYNOPSIS

       command-not-found {binary_name} {repository}

ARGUMENTS

       The following arguments are required:

       binary_name
	   The name of binary you are looking for.

       repository
	   The name of repository for search. For most cases, use zypp

DESCRIPTION

       command-not-found handler is designed to tell users which package contains a missing command.

       The handler is integrated to bash(1) and zsh(1) shells and is not necessary to call it directly. Just type a name of the command in your
       favourite shell and you'll get a result.

       If you consider c-n-f handler useless, just add unset command_not_found_handle to your profile or remove the command-not-found package.

       Handler doesn't call the command-not-found binary directly, it only prints info about it. If you want to invoke it automatically, just add
       export COMMAND_NOT_FOUND_AUTO=1 to your bash profile.

EXAMPLE
: NORMAL USAGE
       For example you want to try blender, because you have heard that is an amazing program. So just type blender in shell:

	   $ blender

       You get the following output:

	   The program 'blender' can be found in the following package:
	     * blender [ path: /usr/bin/blender, repository: zypp (openSUSE 11.1-0) ]

	   Try installing with:
	       sudo zypper install blender

	   bash: blender: command not found

SEE ALSO

       scout(1)

AUTHOR

       Pavol Rusnak <stick@gk2.sk>
	   Developer

http://gitorious.org/opensus					    08/07/2009						      COMMAND-NOT-FOUND(1)

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